I got the Little Loco a couple of weeks ago after speaking with Ron Sutherland on the phone about what cartridges and system I have. It replaced a Pass Labs Aleph Ono (circa 1998). I have used it with an Ortofon Rondo Red (.5mv output, 6 ohms) and an Audiotechnica ART-9 (.5mv, 12 ohms). Both sound very good but the ART-9 sounds much better (as it did with the Pass).
Remember, no loading with this stage because it is a transimpedance stage so no need.
Compared to the Pass the Little Loco is levels better. Wider, higher, deeper soundstage, separation of instruments is much better, just a more natural, more 3D presentation. Not cheap but money well spent IMO.
I wish there were a list of recommended cartridges for these types of stages, I'd start experimenting